In my copending U.S. patent application Ser. No. 15,304, filed Feb. 26, 1979 (as a continuation of Ser. No. 811,886, filed June 30, 1977, now abandoned), I have shown an adapter device for mating a caulking cartridge or the like with an electric drill or the like, so that while the trigger is squeezed on the resulting unit, caulking or the like will be dispensed in a continuous bead until either the trigger is released or the cartridge becomes empty. This adapter was designed particularly for use with electric drills which have a reverse mode. Accordingly, when dispensing is to be terminated and the cartridge is still partly full, in order to prevent unwanted continued extrusion of the plastic material from the cartridge spout, the user must momentarily switch the electric drill into its reverse mode. This results in backing-up of the cartridge piston, thus relieving internal pressure in the cartridge and terminating dispensing.
Such a device works well, but has somewhat limited appeal due to the fact that the most widely-used electric drills in the relevant market do not have a reverse mode.
Separate reversers are commercially available as adapters for such electric drills, but incorporation of one of these in the above-described unit, in which the electric drill, adapter and cartridge are all in one line tends to make the unit too long for some potential users to conveniently handle and operate.
It is also true that the adapter of Ser. No. 15,304 was designed to work with a cartridge of a non-standard type, e.g. not with the familiar push-in rear end wall piston-type cartridge of commerce, but with a twist top-type cartridge with an internal lead screw-mounted piston, e.g. of the type shown in my earlier U.S. Pat. No. 4,144,988, issued Mar. 20, 1979.
Although cartridges of the twist top variety have proved popular in the marketplace, because they may be used alone, i.e. without a caulking gun, I have become impressed with the fact that it would be wise to find a way to make the power caulker concept available for use by persons who would rather use it with the familiar push-in rear wall piston-type cartridge of commerce.
Accordingly, I made the invention now disclosed and claimed in my copending U.S. patent application Ser. No. 75,241, filed Sept. 14, 1979. The preferred unit described therein works with a standard caulking cartridge, incorporates a reverser unit for electric drills which have no built-in reverse mode, and has an S-shaped drive train so that the unit is not necessarily so long as the unit described in Ser. No. 15,304.
In any of these prior units, a reversal takes a finite time to let off pressure, so that a small, but unwanted amount of plastic material usually gets dispensed after the user wants to terminate the dispensing. In units where the electric drill has no built-in reverse mode, the provision of an add-on reverser is, I have come to believe, an unnecessarily slow and expensive way to accomplish the desired result.
Accordingly, I have developed the unit and components of the present invention.